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Saltwater Aquarium

Is that a fish fillet down there on the seabed?  It could be! In our aquariums you’ll find the fish you know and some more unusual creatures from the North Sea. Including plaice…

The ramp to the Aquarium draws you down and leads almost imperceptibly down to below sea level.  Bright-coloured fish and the constantly shifting herring shoal catch your eye.  Try finding the flat fish hiding in or on the seabed. It’s hard work!

In the Aquarium, the tempo is slow.  The wooden panels frame amazing living scenes, while the ceramic artwork echoes the curving shapes of eel and octopus.  You feel almost at home here – but what’s that?  A lesser spotted dogfish glides slowly past in the petting pool.  You hesitate for a moment, then gently stroke its back.

Most of the creatures that inhabit Danish waters are here in our saltwater aquariums.  Many begin their life as fry in the Wadden Sea, then migrate into deeper water.  An overview exhibit gives you a picture of the different North Sea fishing methods. Find out more about the sea creatures in our Aquarium guide – or ask the Aquarium staff.

Direct from the sea to the oceanarium

The large aquarium – the oceanarium in the background – holds about 100,000 litres of salt water pumped in from the Wadden Sea. The observation pane is 3 x 8 metres and about 10 centimetres thick.  Here in the oceanarium you’ll find lesser spotted dogfish, thornback rays, halibut, cod, conger eels, bream, and sea trout.

Come beneath the surface

Welcome to Denmark’s finest touch pool, where you can glide your hands over a ray or a lesser spotted dogfish.

The technology behind the aquarium
The Saltwater Aquarium in the Fisheries and Maritime Museum is made up of two independent systems – a quarantine tank and an exhibition tank. Each one’s water supply is independently treated. Both tanks are supplied with sea water pumped in beneath the museum from the Wadden Sea.
First, a drum filter removes from the incoming seawater all impurities larger than 60 microns. Then the water is put through a protein skimmer to remove any protein, and dyestuffs are burnt off with ozone. Any remaining impurities are caught with sand filters. Now only dissolved substances such as nitrites are left. These are converted to nitrate in our elevated tank which works as a biofilter. The water is then irradiated with ultra-violet light to kill viruses, bacteria and algae.

The Aquarium’s salt water is cooled to 14°C and is continually oxygenated, and the salt content is adjusted to roughly 30 parts per thousand. Its pH value is about 8 and lime and various trace elements are added as required. The temperature of 14°C is a compromise – some of the Aquarium creatures prefer it warmer, others from deeper waters in the North Sea would like it colder.

The exhibition tank holds approximately 300,000 litres of water. The water is circulated around the plant 24 hours a day at approximately 130,000 litres per hour. Our objective is to change all the aquariums’ water once every hour. Approximately 10 per cent of the water is replaced every week.

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